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Encoding to H.264 from DNxHD with Squeeze 7

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Brent Hurlock
Encoding to H.264 from DNxHD with Squeeze 7
on Nov 16, 2011 at 1:54:29 am

Lately I've been having issues encoding from Avid DNxHD 1280x720 .mov files to H.264 files. The audio slips, and gets progressively worse (i.e. later) throughout the length of the show. I've tried the same file on a PC with Squeeze 7 and a Mac with Squeeze 7 and I'm getting the same result. However, I can encode a WMV with the same source MOv just fine. The MOV looks fine too.. Whats going on???

This has happened with a couple of different files now over the last few weeks.
Please help.

Brent


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Ronn Kilby
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 16, 2011 at 3:15:10 pm

I just export an h.264 file from Quictime Pro. Much better than Squeeze.


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Job ter Burg
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 16, 2011 at 8:45:49 pm

QT Pro and H264 will give you a very severe gamma shift.


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Ronn Kilby
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 16, 2011 at 8:47:31 pm

Sorry Job - have to disagree. I do it every day with no shift. I'd be glad to send you some samples.


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Job ter Burg
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 16, 2011 at 9:06:53 pm

Then you must be the only one in the world not suffering from issues with Apple's H264 codec.


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Ronn Kilby
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 16, 2011 at 9:23:54 pm

Perhaps I am (or was that sarcasm? Ouch. Send an email address to H264@kilby.tv and I'll send you a link to download "before and after" of the same clip. Then you can decide.


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Ronn Kilby
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 16, 2011 at 10:36:22 pm

Here ya go Job:
https://www.yousendit.com/sharedFolder?phi_action=app/orchestrateSharedFold...

The DNxHD file was exported from Media Composer then loaded into QT Pro. The H.264 file was exported from there. I do this every day for dozens of TV stations and never one complaint. I have also done this with long form work (a 96 minute feature film) with no gamma shifts, no audio "slipping."

Comments welcome.


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Job ter Burg
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 16, 2011 at 11:16:53 pm

Ronn, yes, sorry about the sarcasm.

Your examples, however, do show a gamma shift.

Your DNxHD appears to have been exported with stretched levels, so it runs 0-255 (not broadcast legal). The H264 appears to be broadcast legal. Rescaling one of them (I corrected the DNxHD back to 16-235), and comparing two frames shows quite a different gamma, most notably in the details in the sky of the H264. (BTW, I'm using AMA to link to your files, and use Source Settings to compensate the DNxHD back to 16-235).

But even at desktop level, the very first frame of your spot demonstrates the issue. The symbol above the World Cup logo looks fine in DNxHD, but is only half visible in the H264 (where it blends to full white with the 'hot' sky).

The issues with QT and some codecs (ProRes, H264) have been popping up everywhere on forums like these over the past few years.

I haven't managed to export to H264 without any gamma shifts, but there was much less of a shift when using the Main Concept H264 encoder that is featured in Squeeze.

IMO, the best way to export a file for broadcast, with correct levels, is to avoid QrapTime, and export as Op1A MXF (Export to a virtual XDCAM device).


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Job ter Burg
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 16, 2011 at 11:36:13 pm

My favorite test chart by the way:

http://www.belle-nuit.com/testchart.html

Import this into your Avid without modifying levels (choose 709), and you will have a great test chart with legal and illegal levels. Nice one to carry through your workflow and see if you can preserve accurate levels throughout.


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Ronn Kilby
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 17, 2011 at 12:42:03 am

Thanks for setting me straight, Job (no sarcasm intended) - I'll have to return the money I've been paid for all those spots. (Not really). I'll have to try out those test charts when I have some downtime - maybe next year.


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Ra-ey Saleh
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 17, 2011 at 2:19:40 am

As Job has detailed perfectly, the H.264 Gamma Shift if pretty famous and very annoying. It's more prevalent with files created on a PC as well.
And the MainConcept H.264 encoder that is in Squeeze 7 upwards is really a thing of beauty. Stunning and no real Gamma Shift (or at least not really noticable)...
You can download some presets here that might be a good starting point:
http://exchange.sorensonmedia.com/

Ra-ey


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Ronn Kilby
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 17, 2011 at 5:15:04 am

Thanks Ra-ey - I just purchased the Squeeze 8 upgrade but have not yet installed. Could you specify a particular preset that would be optimal for DNxHD to H.264 HD?


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Ra-ey Saleh
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 17, 2011 at 5:31:29 am

What's the source spec and destination spec you want and I'll see if there's a preset already made.

Ra-ey


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Ronn Kilby
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 17, 2011 at 3:18:33 pm

1920x1080 59.84i DNxHD to 1920x1080 59.84i H.264, best quality.


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Ra-ey Saleh
Re: Encoding to H.264 from DNxHD with Squeeze 7
on Nov 18, 2011 at 1:33:57 am

Ronn,
I've tweaked a preset I downloaded from Sorenson Exchange by Coby Rich to make it Interlaced for you.
Just double-click the file and install it in the default location. You'll find it when you open up Sorenson in the Favourites tab.
I set the Audio to 44, but you can easily change it to 48.
Also, tweak any other settings you want.
Let us know if it works for you.
3272_mp4mainconcepthd1080i.spfx.zip

ps. I used the original preset to encode my reel and got much better results than using any other encoder (i.e. Compressor, Streamclip). Have a look (shameless plug!)


Ra-ey


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